Infusion pump

ABSTRACT

An infusion pump includes a housing having a compartment structured to receive a syringe and a drive mechanism supported by the housing. The drive mechanism is structured and arranged to contact a syringe plunger of the syringe and move the syringe plunger within a syringe barrel of the syringe. The infusion pump further includes a syringe plunger position sensor and a syringe barrel size sensor. The sensors each include a magnet positioned on the drive mechanism and a magnetic sensor array supported by the housing.

PRIORITY CLAIM

This application is a continuation of U.S. patent application Ser. No.12/573,620, entitled Infusion Pump With Battery Operation Capability,filed Oct. 5, 2009, which is continuation of U.S. patent applicationSer. No. 11/319,350, entitled Infusion Pump, filed Dec. 28, 2005, nowU.S. Pat. No. 7,608,060, issued Oct. 27, 2009, which is a divisional ofU.S. patent application Ser. No. 10/172,807, entitled Infusion Pump,filed Jun. 14, 2002, now U.S. Pat. No. 7,018,361, issued Mar. 28, 2006.

BACKGROUND

The present invention relates to a pump and more particularly to aninfusion pump for the delivery of a medication to a patient.

Generally, medical patients sometimes require precise delivery of eithercontinuous medication or medication at set periodic intervals. Medicalpumps have been developed to provide controlled drug infusion whereinthe drug can be administered at a precise rate that keeps the drugconcentration within a therapeutic margin and out of an unnecessary orpossibly toxic range. Basically, the medical pumps provide appropriatedrug delivery to the patient at a controllable rate which does notrequire frequent attention.

Medical pumps may facilitate administration of intravenous therapy topatients both in and outside of a clinical setting. Outside a clinicalsetting, doctors have found that in many instances patients can returnto substantially normal lives, provided that they receive periodic orcontinuous intravenous administration of medication. Among the types oftherapies requiring this kind of administration are antibiotic therapy,chemotherapy, pain control therapy, nutritional therapy, and severalother types known by those skilled in the art. In many cases, patientsreceive multiple daily therapies. Certain medical conditions requireinfusions of drugs in solution over relatively short periods such asfrom 30 minutes to two hours. These conditions and others have combinedto promote the development of increasingly lightweight, portable orambulatory infusion pumps that can be worn by a patient and are capableof administering a continuous supply of medication at a desired rate, orprovide several doses of medication at scheduled intervals.

Configurations of infusion pumps include elastomeric pumps, whichsqueeze solution from flexible containers, such as balloons, into IVtubing for delivery to the patient. Alternatively, spring-loaded pumpspressurize the solution containers or reservoirs. Certain pump designsutilize cartridges containing flexible compartments that are squeezed bypressure rollers for discharging the solutions, such as in U.S. Pat. No.4,741,736. Other references which disclose portable infusion pumpsinclude U.S. Pat. No. 5,330,431 (showing an infusion pump in whichstandard pre-filled single dosage IV bags are squeezed by the use of aroller); U.S. Pat. No. 5,348,539 (showing an infusion pump in whichprepackaged IV bags are squeezed by a bladder which is actuated by fluidpumped from a reservoir); U.S. Pat. No. 5,429,602 (showing aprogrammable portable infusion pump system for injecting one or moremedicinal substances into an individual); and U.S. Pat. No. 5,554,123(showing an infusion pump in which the amount of fluid required to pumpa bladder sufficient to fully dispense solution from a bag is less thanthe volume of an IV bag.). Infusion pumps utilizing syringes are alsoknown wherein a drive mechanism moves a plunger of the syringe todeliver fluid to a patient. Typically, these infusion pumps include ahousing adapted to receive a syringe assembly, a drive mechanism adaptedto move the syringe plunger, a pump control unit having a variety ofoperating controls, and a power source for powering the pump includingthe drive mechanism and controls.

While the discussed prior art and other designs have recognized the needfor an infusion pump which is smaller and more compact for mobile use byambulatory patients or other patients, each has failed to address theneed for a more suitable power source. Naturally, a portable pump mustbe supplied with an equally portable power source as a means forpowering the pump motor. Batteries are a suitable choice of power forportable units. Some prior art pumps may use disposable batteries whileother pumps may use rechargeable batteries.

Disposable batteries have proven to have a longer life than the life ofa rechargeable battery (with a single charge). Disposable batteries arealso typically smaller than rechargeable battery units. However, thereis an environmental disposal concern with such batteries, as they placea considerable burden on the environment. Disposable batteries areresponsible for a major share of heavy metal pollution in domesticwaste. Despite special collection efforts and consumer awarenesscampaigns, a high percentage of batteries sold still end up in domesticwaste sites. Heavy metals eventually leak from the batteries into theground soil, damaging the environment.

Environmental concerns are greatly alleviated if rechargeable batteriesare used in place of disposable batteries. However, where such batteriesor battery packs are rechargeable, an AC outlet is usually necessary. Aseparate charger, as is well-known in the art, is also required for therecharging effort. Unfortunately, these facilities are not alwaysreadily available or accessible to the patient and, with respect to theusual adapters and extension cords, they add to the bulk and weight ofthe infusion pump system. Furthermore, in certain pumps utilizingrechargeable batteries, the pump itself must be used in the rechargingeffort as it typically houses the transformer used in the rechargingprocess.

Batteries and battery packs that are large and bulky significantly addto the weight of the portable infusion pump. Weight and size of theinfusion pump is an important consideration because it may be carriedabout by nurses or other hospital personnel. The pump must also be sizedto be attached to an I.V. pole. The I.V. pole, with attached pump, maybe moved about in a hospital setting. In addition, where interruptedoperation of the pump may have negative consequences, extra batteries oran extra battery pack may be added to the carrying necessities of theinfusion pump. In some instances, the carrying of a second set ofbatteries or a back-up battery pack may double the weight of the powersource.

Thus, there is seen in the prior art advantages and disadvantages toboth disposable and rechargeable battery powered pumps. It should beunderstood that under certain circumstances, a pump that uses disposablebatteries may be preferable or the only option available (if no outletis available). Under other circumstances, the benefits of lower cost andenvironmental concerns may dictate that rechargeable batteries arepreferred.

In addition to the above, customs and/or regulations of differentsovereigns may dictate the use of one type of power source for a pumpover another. For example, in the U.S., pumps powered by disposablebatteries have long been preferred due to their convenience and abilityto provide power for extended periods of time. On the other hand, inEurope, rechargeable battery powered pumps are preferred, due toenvironmental concerns with the disposal of battery waste.

In light of the advantages and disadvantages that both disposable andrechargeable batteries provide, it may be desirable for some toalternate use of both battery types. However, it can be easilyrecognized that it would prove burdensome and a waste of space andresources to supply or have on hand two separate pumps, each utilizing adifferent battery type.

It may also be desirable for manufacturers of pumps to satisfy the needsof users of rechargeable battery powered pumps as well as disposablebattery powered pumps. However, it is costly for manufacturers of pumpsto manage entirely separate lines of pump types or forego supplying onepump type over another. Thus, it is recognized that several advantagesexist for a pump that can utilize both disposable and rechargeablebatteries. There exists a need in the art for a pump that may utilizeboth disposable and rechargeable batteries. There also remains a needfor a pump that utilizes rechargeable batteries that can be re-chargedwithout the use of the pump.

Additional problems have also been experienced with infusion pumps. Forexample, certain sensing systems that detect whether an occlusion ispresent in an infusion line have proven to be unreliable or too complexin construction. Certain syringe plunger position detectors and syringebarrel size detectors have also proven to be unreliable. In addition,drive mechanisms for syringe plungers have also proven to be unreliableas certain components become stripped or jammed adversely affecting themechanism.

The present invention is provided to solve these and other problems.

SUMMARY

The present invention is generally directed to an infusion pump fordelivering a flowable material, such as a fluid medication, to a patientthrough an infusion line.

According to one aspect of the invention, the infusion pump isconfigured to be powered by either a disposable battery or arechargeable battery. The infusion pump has a housing having a recess. Amotor is positioned within the housing and is operably connected to anelectrical contact disposed in the recess. The motor powers the pump.The recess is adapted to receive one of a disposable battery unit and arechargeable battery unit.

According to another aspect of the invention, the rechargeable batterymay be in the form of a rechargeable battery unit. The rechargeablebattery unit has a transformer positioned within the unit. A conductiveelement for providing power from an AC power outlet is coupled to thetransformer. A switch is provided for receiving a first electronicsignal indicative of whether the conductive element is providing powerto the AC power source. A DC power source signal is provided by said ACpower outlet and rectifying circuitry. A rechargeable battery sourcesignal is provided from a receptacle within said rechargeable batteryunit. The switch connects the DC power source signal to output terminalsof the rechargeable battery unit only if the first electrical signalindicates that the conductive element is not providing power from the ACpower source.

According to another aspect of the invention, the infusion pump isadapted to receive a syringe having a syringe barrel moveably receivinga syringe plunger therein. The infusion pump has a housing defining acompartment adapted to receive the syringe. The compartment has a rearwall. The housing further has a curved lip generally adjacent to therear wall. A clamp is connected to the housing and is positioned in thecompartment in confronting relation to the rear wall. The syringe can beloaded into the compartment between the rear wall and the clamp whereinupon initial insertion, the curved lip is adapted to slidingly engagethe syringe barrel allowing generally one-hand loading of the syringeinto the compartment. Syringes of a variety of different sizes can beloaded into the pump in this fashion. The curved lip has a lengthgenerally in correspondence with a length of the syringe barrel adaptedto be received in the compartment. The clamp is slidable by rollerspositioned at one end of the clamp.

According to another aspect of the invention, the infusion pump has ahousing having a compartment adapted to receive a syringe having abarrel and a plunger. A drive mechanism is supported by the housing andis adapted to contact the plunger to move the plunger within the barrel.The drive mechanism further has a linearly moveable arm having a loadcell mounted thereon. A load beam is pivotally connected to the arm. Theload beam has one side contacting the load cell and another side adaptedto contact the plunger. Upon movement of the arm to move the plunger,the load cell senses a reactive force from the load beam. The load cellconverts the force into a usable signal wherein an occlusion is signaledif the usable signal is outside a predetermined acceptable range.

According to another aspect of the invention, the infusion pump has asyringe plunger position sensor and a syringe barrel size sensor. Eachsensor utilizes a magnet/linear sensor array assembly.

According to a further aspect of the invention, the drive mechanism hasa lead screw rotatably connected to a motor. A slide assembly has athreaded member wherein the threaded member is associated with the leadscrew. The arm has one end connected to the slide assembly and one endadapted to be engaged with the syringe plunger. The threaded member isrotatably biased in engagement with the lead screw, wherein uponrotation of the lead screw by the motor, the slide assembly linearlymoves the arm wherein the arm is adapted to move the syringe plungerwithin the syringe barrel. In one preferred embodiment, the threadedmember is a rotary nut.

According to another aspect of the invention, the infusion pump hasimproved communication capabilities. The pump has a user interfacehaving a memory for storing infusion data. The pump has a data portwherein infusion data can be transferred via infrared communication fromthe pump to a personal digital assistant.

Other features and advantages of the invention will be apparent from thefollowing specification taken in conjunction with the followingdrawings.

BRIEF DESCRIPTION OF THE FIGURES

To understand the present invention, it will now be described by way ofexample, with reference to the accompanying drawings in which:

FIG. 1 is a front perspective view of one embodiment of an infusion pumpwhich may be configured in accord with and embody the present invention;

FIG. 2 is another front perspective view of the infusion pump of thepresent invention with an access door removed;

FIG. 3 a is a front elevation view of the infusion pump of the presentinvention;

FIG. 3 b is another front elevation view of the infusion pump of thepresent invention mounted in an alternative configuration;

FIG. 4A is a rear perspective view of the infusion pump of the presentinvention, showing a rechargeable battery unit associated therewith;

FIG. 4B is a rear perspective view of the infusion pump of the presentinvention, showing a disposable battery unit associated therewith;

FIG. 5 is another rear perspective view of the infusion pump of thepresent invention with the battery unit removed;

FIG. 6 is a rear elevation view of the infusion pump of the presentinvention;

FIG. 7 is a side elevation view of the infusion pump of the presentinvention;

FIG. 8 is an opposite side elevation view of the infusion pump of thepresent invention;

FIG. 9 is a perspective view of the rechargeable battery unit shown inFIG. 4A;

FIG. 10 is a side elevation view of the rechargeable battery unit shownin FIG. 9;

FIG. 11 is an end elevation view of the rechargeable battery unit shownin FIG. 9;

FIG. 12 is a electrical schematic view of the rechargeable battery unit;

FIG. 13 is a perspective view of the disposable battery unit shown inFIG. 4B;

FIG. 14 is a schematic view of a syringe drive mechanism and occlusionsensor for the infusion pump of the present invention;

FIG. 15 is partial perspective view of the syringe drive mechanism andfurther showing a syringe plunger position indicator;

FIG. 16 is a partial plan view of the syringe drive mechanism andfurther showing the syringe plunger position indicator;

FIG. 17 is a partial plan view of the syringe plunger positionindicator;

FIG. 18 is a perspective underside view of the syringe drive mechanismand further showing a syringe barrel size indicator;

FIG. 19 is an enlarged partial perspective view of a syringe barrelclamp of the infusion pump of the present invention;

FIG. 20 is partial perspective view of a video display and padassociated with a user interface of the infusion pump of the presentinvention;

FIG. 21 is a partial cross-sectional view of the video display mountedin a housing of the infusion pump;

FIG. 22 is a partial perspective view of the syringe drive mechanism;

FIG. 23 is a partial cross-sectional view of the syringe drivemechanism;

FIG. 24 is a partial perspective view of a slide assembly of the syringedrive mechanism having a rotary nut in a disengaged position;

FIG. 25 is a cross-sectional view of the slide assembly of FIG. 24 in adisengaged position;

FIG. 26 is a partial perspective view of the slide assembly wherein therotary nut is in an engaged position;

FIG. 27 is a cross-sectional view of the slide assembly of FIG. 26 in anengaged position;

FIG. 28 is a perspective view of the rotary nut;

FIG. 29 is an elevation view of the rotary nut;

FIG. 30 is an underside perspective view of the rotary nut;

FIG. 31 is a schematic wiring diagram of a patient controlled analgesiabutton associated with the pump of the present invention, the buttonbeing in an at rest position;

FIG. 32 is another schematic wiring diagram of the patient controlledanalgesia button associated with the pump of the present invention, thebutton being in an actuated position;

FIG. 33 is a table summarizing information revealed by the circuitsassociated with the button of FIGS. 31 and 32

DETAILED DESCRIPTION

While the present invention is susceptible of embodiment in manydifferent forms, there is shown in the drawings and will herein bedescribed in detail preferred embodiments of the invention with theunderstanding that the present disclosure is to be considered as anexemplification of the principles of the invention and is not intendedto limit the broad aspect of the invention to the embodimentsillustrated.

Referring to FIG. 1, therein is shown one embodiment of an infusion pumpof the present invention generally referred to with the referencenumeral 10. The infusion pump 10 generally includes a housing 12 thatsupports a syringe assembly 14, a user interface 16, a power supply 18,a drive mechanism 20 having an occlusion sensor 22 (FIG. 14), and asyringe sensor system 24 (FIGS. 15-18).

While the present invention discloses a portable infusion pump, such as,for example, a syringe-based infusion pump, and their progeny, designedand manufactured by Baxter International, Inc. of Deerfield, Ill., it isunderstood that individual aspects of the invention that can beincorporated into other types of pumps or other electrical or medicaldevices.

As shown in FIGS. 1 and 2, the housing 12 of the pump 10 has a generallycontoured shape. The housing 12 includes a first member 26 and a secondmember 28 that are connected together to form a central cavity 30. Thecentral cavity 30 houses various components of the pump 10 including theuser interface 16. The first member 26 of the housing has an opening 32that accommodates a display screen of the user interface 16. As shown inFIG. 5, a rear portion of the housing 12 has a receptacle or recess 33that is adapted to receive the power supply 18 to be described ingreater detail below. At a bottom, front portion of the housing 12, acontainer compartment or syringe compartment 34 is defined thataccommodates the syringe assembly 14, a portion of the drive mechanism20 and other components. The first member 26 of the housing 12 has ahinged access door 36 that encloses the syringe assembly 14 in thecompartment 34. The access door 36 is preferably transparent in orderfor medical personnel to view the contents in the syringe assembly 14. Alock 38 is provided with the door 36 to prevent unauthorized access tothe syringe assembly 14. The lock 38 is required because oftentimesdrugs such as morphine are infused by the pump 10 and can beunfortunately subject to theft. An upper portion of the housing 12 isprovided with a handle 40. The housing 12 can be made from a variety ofmaterials including various types of plastics and metals. As shown inFIG. 4-8, the housing 12 has a pole clamp 42 attached to the secondmember 28 of the housing 12. The pole clamp 42 can have various designsand is adapted to mount the pump 10 on a pole assembly such as used in ahospital setting. In a preferred embodiment, the pole clamp 42 isadapted to be able to mount the pump 10 in various positions. Forexample, the pump 10 can be mounted in a generally horizontal positionshown in FIG. 3 a or a generally vertical position shown in FIG. 3 b.

FIG. 2 discloses the syringe compartment 34 in greater detail.Generally, the syringe compartment 34 is dimensioned to receive andsupport the syringe assembly 14 as well as receive a portion of a pumpactuator such as the drive mechanism 20. Briefly, the syringe assembly14 generally includes a syringe barrel 46 and a medical fluid membersuch as a syringe plunger 48. The syringe barrel 46 contains medicationand slidably receives the syringe plunger 48. The syringe plunger 48 isdriven by the drive mechanism to force medication from the syringebarrel 46 through a tube (not shown) and to a patient. The tube wouldhave one end connected to an end of the syringe barrel 46 and anotherend adapted to be connected to a patient.

The syringe compartment 34 has a rear wall 44 that is generally concaveto receive the syringe barrel 46 of the syringe assembly 14. The syringebarrel 46 of the syringe assembly 14 and rear wall 44 are generally inconfronting relation. The housing 12 further has a curved lip 50 that ina preferred embodiment is integral with the rear wall 44. The lip 50aids in loading a syringe assembly 14 in the compartment 34 to bedescribed in greater detail below. As shown in FIGS. 2 and 19, a syringeclamp 52 is movably mounted in the compartment 34. The clamp 52 has aconcave inner surface that faces the rear wall 44 and that fits over thesyringe barrel 46. As shown in FIG. 18, the clamp 52 is slidable along arod assembly 54 to move the clamp 52 towards and away from the rear wall44. The clamp 52 can slide along the rod assembly 54 to accommodatedifferent sized syringe barrels. As shown in FIG. 19, a base portion ofthe clamp 52 has a pair of rollers 56,58 that help reduce friction whenthe clamp 52 slides along the housing 12. Due to tolerances, the clamp52 may also pivot slightly. The clamp 52 is resiliently biased towardsthe rear wall 44. The housing 12 and syringe compartment 34 are sizedsuch that an entire syringe assembly, with plunger fully extended fromthe syringe barrel, is contained within the housing and can be enclosedby the access door 36. No part of a syringe barrel or syringe plungerprotrudes from the housing 12. A portion of the drive mechanism 20extends into the syringe compartment 34 to engage the plunger 48. Theaccess door 36 has an opening to accommodate the tube (not shown) thatis attached to the syringe barrel 46 to deliver medication to thepatient.

As shown in FIGS. 1-3, the pump has a user interface 16. Portions of theuser interface 16 are described in greater detail in commonly-owned U.S.patent application Ser. No. 10/172,808 entitled “System And Method ForOperating An Infusion Pump,” publication number 20040225252, nowabandoned, filed concurrently herewith and incorporated by referenceherein. The user interface 16 generally includes a display screen 60, afirst control panel 62 and a second control panel 64, and associatedelectrical components and computer software contained within the housing12 to operate the pump 10. The display screen 60 displays all of thegeneral operating parameters of the pump 10 and fits within the opening32 in the housing 12. The display screen 60 also acts as a touch screenfor data to be inputted into the pump 10 by a user. As discussed, thepump 10 can be mounted in either a generally horizontal position (FIG. 3a) or a generally vertical position (FIG. 3 b). The software associatedwith the user interface 16 has the ability to display information on thescreen 60 in either a landscape orientation or a portrait orientation.When the pump is mounted in the horizontal configuration as shown inFIG. 3 a, information is displayed on the display screen 60 in alandscape configuration. Conversely, when the pump 10 is mounted in thevertical configuration as shown in FIG. 3 b, information is displayed onthe display screen 60 in a portrait configuration. Thus, depending onhow the pump 10 is mounted, the information can be read by users withoutthe need to tilt one's head. This feature is described in greater detailin commonly-owned U.S. patent application Ser. No. 10/172,804 entitled“Dual-Orientation Display For Medical Devices,” filed concurrentlyherewith, and incorporated by reference herein. The first control panel62 generally has a start button 66, a stop button 68 and an alarm/alertbutton 70. The second control panel 64 generally has a settings panel72, a history button 74 and a data port 76. These controls will bedescribed in greater detail below.

The pump 10 and user interface 16 may utilize additional identificationfeatures regarding the medication delivered by the pump 10. For example,and as shown in FIG. 2, the pump 10 may be equipped with an RFID (radiofrequency identification) reader 86 that cooperates with an RFID tag 88attached to the syringe barrel 46. The RFID tag 86 has a transpondercircuit and an antenna circuit. The RFID tag 86 can store significantinformation including, but not limited to, the type of medication,amount, concentration, as well as pumping parameters and instructionsfor the medication. The RFID reader 86 has energizer, demodulator anddecoder circuits. The energizer circuit emits a low-frequency radio wavefield that is used to power up the RFID tag 88. This allows the tag 88to send its stored information to the reader 86. The information isdemodulated and decoded where it then can be used by the computerassociated with the user interface 16. While several differentconfigurations are possible, the RFID reader 86 can be mounted in pumphousing adjacent the syringe compartment 34. The RFID tag 88 is affixedgenerally to the syringe barrel 46. When the syringe assembly 14 isproperly inserted into the pump 10, the RFID reader 86 automaticallyreads the information from the RFID tag 88, which can be used to aid inproperly operating the pump 10 for a particular patient. It isunderstood that other types of data reader/data carrier systems can alsobe used.

As shown in FIGS. 20 and 21, the display screen 60 is equipped with apad 78 about the outer periphery of the screen 60. The pad 78 is a shockabsorbent member made preferably of an elastomeric material. In onepreferred embodiment, the pad 78 is made from polyurethane. The pad 78has a face 80 that is positioned between the display screen 60 and aninner surface 82 of the first member 26 of the housing 12. The pad 78also has a sidewall 84 preferably integral with the face 80. The pad 78absorbs forces generated if the pump 10 is jostled, bumped or dropped,and minimizes the effect such occurrences have on the display screen 60.The pad 78 also resists fluid infiltration into the housing 12.

The pump 10 of the present invention includes the power supply 18 thatcan take many different forms. In one preferred embodiment, the powersupply 18 may be in the form of a rechargeable battery unit 90 or adisposable battery unit 92. The rechargeable battery unit 90 isgenerally shown in FIG. 4 a and the disposable battery unit 92 isgenerally shown in FIG. 4 b. The pump 10 will operate with either unit90,92 depending on the needs and desires of the user. As shown in FIG.5, the pump 10 has an electrical contact 94 positioned in the recess 33that is in electrical communication with the user interface componentsof the pump 10 as is known. The contact 94 will cooperate with acorresponding electrical contact on either of the rechargeable batteryunit 90 or the disposable battery unit 92 as will be described.

FIGS. 4 a and 6-12 generally disclose the rechargeable battery unit 90.FIGS. 9-11 show the rechargeable battery unit 90 removed from the pump10. As shown in FIGS. 4 a and 11, the rechargeable battery unit 90generally includes a battery housing 96 having an electrical contact 98to cooperate with the pump housing electrical contact 94, a rechargeablebattery 100, associated electrical components 102, and an AC powersupply assembly 104.

As shown in FIGS. 9-11, the rechargeable battery unit housing 96generally has a base member 106 and a cover member 108. The base member106 and cover member 108 are contoured wherein the housing 96 has ashallow first end 110 and a deeper second end 112. The contour of thehousing 96 is generally similar to the outer contour of the backside ofthe pump housing 12. FIG. 4 a, 6-8 show the unit 90 installed in thepump housing 12 illustrating the corresponding contours. As shown inFIG. 11, a bottom portion of the base member 106 supports the electricalcontact 98, and contacts the housing electrical contact 94 when the unit90 is installed. As further shown, the battery unit housing 96 has apair of posts 114 that laterally protrude from the housing 96. The posts114 cooperate with retainers in the pump housing 12 to retain the unit90 within the housing 12. A push button 116 is included on the housingcover 108 to retract the posts 114 when removing the unit 90 from thepump housing 12.

As further shown in FIGS. 9 and 10, the AC power supply assembly 104 hasa power cord 118 and an associated terminal 120 that plugs into thehousing 96. The AC power supply assembly 104 has a plug that can beinserted into a standard electrical outlet to recharge the rechargeablebattery 100 when necessary. AC power can also be supplied through theassembly 104 to power the pump 10.

FIG. 12 schematically shows the electrical components 102 that areassociated with the rechargeable battery unit 90. The electricalcomponents 102 generally include a power supply 122 and a rechargerassembly 124 that includes a recharger 126 and a diode mechanism in theform of a first diode 128 and a second diode 130. The power supply 122,in one preferred embodiment, is an off-line switching power supply. Thepower supply 122 generally includes a field-effect transistor (FET) 132,connected to a transformer 134, which in turn is connected to a powersupply diode 136. The power supply 122 has one connection to the ACpower supply assembly 104. The power supply 122 is also connected to therecharger 126. The diodes 128,130 are generally connected to therecharger 126, the power supply 122, the rechargeable battery 100 andthe terminal 98 so as to provide the desired power through the unit 90.For example, when the plug of the AC power supply assembly 104 is notplugged into a wall outlet as shown in FIG. 12, the first and seconddiodes 128,130 are biased and configured such that power is beingsupplied by the rechargeable battery 100. If the plug of the assembly104 is plugged into a wall outlet, the power supply 122 provides 12volts. When the 12 volts are sensed, the diodes 128, 130 are configuredsuch that the rechargeable battery 100 is being recharged by the powersupply 122 and the unit 90 is supplying power through the power supply122 via the plugged in AC power supply assembly 104. Accordingly, powercan be switched from being supplied from the rechargeable battery 100 orfrom the wall outlet. It is further noted that because the rechargeablebattery unit 90 houses the power supply 122, the recharger 126 and therechargeable battery 100 within the unit 90, the battery 100 can berecharged without the use of the pump 10. The battery 100 can be chargedsimply by plugging the cord of the power assembly 104, connected to theunit 90, into a wall outlet. The unit 90 need not be installed into thepump 10. In prior art pumps, the pump itself is needed to recharge thebattery. It is also understood that the rechargeable battery unit 90 canbe defined without the AC power cord assembly 104 wherein the assembly104 is considered a separate component removably attachable to the unit90. The battery units 90,92 may also be equipped with a microchip thatis capable of transmitting data to the user interface 16 of the pump 10such as the amount of charge left in the batteries being utilized.

FIGS. 4 b and 13 generally disclose the disposable battery unit 92. Thegeneral structure of the disposable battery unit 92 is similar to therechargeable battery unit 90. The disposable battery unit has a housing142 having an electrical contact 144 that will cooperate with thehousing electrical contact 94 in the housing recess 33 (See FIGS. 4 band 5). The housing 142 has a base member 146 and a cover member 148.The base member 146 receives a plurality of disposable batteries 150,and in a preferred embodiment, four D-cell batteries are utilized. It isunderstood, however, that other battery configurations are possible. Thebatteries are supported such that the batteries will supply electricalpower through the contact 144 as is known. As shown in FIG. 4 b, thedisposable battery unit 92 is received by the recess 33 of the pump 10in the same fashion as the rechargeable battery unit 90 shown in FIG. 4a.

Thus, depending on the desires of the user, the pump 10 may be poweredby the rechargeable battery unit 90 or the disposable battery unit 92.The pump 10 may be provided with multiple units 90,92 wherein the pump10 can remain in use by replacing the unit 90,92 requiring eitherrecharging, or new disposable batteries.

FIGS. 14, 15 and 22-30 disclose the syringe drive mechanism 20. FIG. 14represents a simplified schematic view. The syringe drive mechanism 20is accommodated by the pump housing 12 and generally includes a motor152, a lead screw 154, a connecting linkage 156 and a slide assembly158. Briefly, the connecting linkage 156 is connected to the slideassembly 158, which is associated with the lead screw 154. The slideassembly 158 which moves linearly in response to rotation of the leadscrew 154 by the motor 152. Linear movement of the connecting linkage156 moves the syringe plunger 48, having a plunger flange 48 a, aplunger arm 48 b and plunger stopper 48 c, within the syringe barrel 46to expel fluid from the syringe assembly 14.

As shown in FIG. 14, the motor 152 is operably connected to the leadscrew 154 to rotate the lead screw 154 when the motor 152 is energized.The lead screw 154 has threads 160 that cooperate with a threaded memberof the slide assembly 158 as will be described in greater detail below.

FIGS. 14-18 and 22 generally show the connecting linkage 156. Theconnecting linkage 156 generally includes a tube member 162 and aplunger engagement arm 164. The tube member 162 is connected at one endto the slide assembly 158 and at another end to the plunger engagementarm 164. As shown in FIG. 22, the tube member 162 houses a rod 166 thatis connected to a lever 168 pivotally mounted on the engagement member164. As explained in greater detail below, the rod 166, when actuated bythe lever 168, can disengage the slide assembly 158 from the lead screw154. This allows the slide assembly 158 to freely slide along the leadscrew 154 to linearly position the plunger engagement arm 164 againstthe plunger 48 extending from the syringe barrel 46.

As further shown in FIGS. 14, 15 and 22-23, the slide assembly 158generally includes a rail member 170 and a slide member 172. The railmember 170 has a pair of legs 174 depending from a cover plate 176. Theslide member 172 slides beneath the cover plate 176 as can beappreciated from FIG. 15. The legs 174 have an inwardly protrudingportion 175. The rail member 170 is positioned within the housing 12 andadjacent the rear wall 44 of the syringe compartment 34.

As shown in FIGS. 22-27, the slide member 172 generally has a base 178and a cover 180 that collectively support a threaded member 182 orrotary nut 182 therein. The base 178 has a countersunk bore 184therethrough that is in communication with a channel 186. The borereceives the rotary nut 182 and the channel 186 accommodates a portionof the rotary nut 182 and the lead screw 154. The base 178 has a pair ofcantilevered beams 188 that correspond in shape to the legs 174 of therail member 170. The beams 188 are slightly biased into frictionalsliding engagement with the legs 174 and provide a smooth slidingmovement of the slide member 172 along the rail member 170. As shown inFIG. 23, the cover 180 fits over the rotary nut 182. The cover 180supports additional structure such as a pin 185 and lock arm 187 (SeeFIG. 24). This structure will be described in greater detail below.

FIGS. 28-30 further disclose the rotary nut 182. The rotary nut 182 is aunitary member having a generally cylindrical base 190. The base 190 hasa lip 192 that engages the countersunk bore 184 in the slide member 172.The base 190 has a first finger 194 and a second finger 196 dependingtherefrom. The fingers 194,196 are spaced to define an opening 197. Theopening 197 receives the lead screw 154. Fingers 194 and 196 have firstand second threaded portions 1989 respectively thereon that engage thethreads 160 on the lead screw 154. Fingers 194 and 196 have first andsecond threaded portions 198 respectively thereon that engage thethreads 160 on the lead screw 154. The threads 198 are positioned ongenerally opposed sides of the rotary nut 182. The base 190 further hasan over-rotation surface 200 and a rotation surface 202.

As further shown in FIGS. 22-27, the rotary nut 182 is received in thecylindrical bore 184 in the slide member 172. The tube member 162 of theconnecting linkage 156 is connected to the base 178 of the slide member172. The slide member 172 is positioned for sliding movement on the railmember 170. The lead screw 154 is routed through the channel 186 in theslide member 172. FIGS. 26 and 27 show the rotary nut 182 in an engagedposition with the lead screw 154. In FIG. 26, the cover 180 of the slidemember 172 is removed for clarity. The rotary nut 182 is rotationallybiased into engagement with the lead screw 154 by a spring 204. Thethreads 198 on each finger 192,194 of the rotary nut 182 engagegenerally opposed sides of the lead screw 154. The over-rotation surface200 engages the pin 185 (carried by the cover 180) to preventover-rotation of the nut 182 into the lead screw 154. This maximizesperformance and minimizes wear of the threads 198 of the rotary nut 182.With the threads 198,160 engaged, when the motor 152 rotates the leadscrew 154, the rotary nut 182 moves along the lead screw 154 which, inturn, linearly moves the slide member 172 and connecting linkage 156.This pushes the plunger 48 into the syringe barrel 46 to displacemedicament from the syringe assembly 14. The lock arm 187 engages thebase 190 of the rotary nut 182 to prevent the rotary nut 182 fromdisengaging under load such as from back pressure from the syringeassembly 14.

The rotary nut 182 can also be easily disengaged from the lead screw 154which allows the slide member 172 to be positioned along the lead screw154 such as when positioning the plunger engagement arm 164 against thesyringe plunger 48. As shown in FIGS. 22, 24 and 25, the lever 168 isrotated on the plunger engagement arm 164. A camming action linearlymoves the rod 166 within the tube member 162. The rod 166 engages therotation surface 202 to rotate the rotary nut 182. The rotary nut 182 isrotated such that the threads 198 become disengaged from the threads 160on the lead screw 154. This allows the slide member 172 to slide freelyalong the rail member 170 to position the plunger engagement arm 164.

The rotary nut 182 provides several advantages over previous nut/leadscrew arrangements using single or multiple half-nuts that engage thelead screw. Half-nuts require a high rate spring to bias the nut intoengagement with the lead screw and prevent disengagement. This requirestransverse side loading of the lead screw that causes wear and mechanisminefficiency. Because the rotary nut 182 is a unitary piece,misalignment problems between two half-nuts is also eliminated. Therotary nut 182 utilizes a positive stop and lock. Therefore, side loads,moments, over engagement and disengagement during pumping are eliminatedand wear is minimized.

The pump 10 is equipped with an occlusion sensor 22 to determine if aninfusion line connected to the syringe barrel 46 is blocked. In onepreferred embodiment of the invention, the occlusion sensor 22 isincorporated into the plunger engagement arm 164 of the drive mechanism20. As shown schematically in FIG. 14, the occlusion sensor 22 generallyincludes a load cell 210 and a load beam 212. The load cell 210 isconnected to a distal end of the plunger engagement arm 164. The loadbeam 212 is connected to generally a mid-portion of the arm 164 througha pivotal connection 214. The load beam 212 has a pusher block 216 thatabuts against the end of the syringe plunger 48. The load cell 210 ispositioned adjacent to and in contact with a distal end 218 of the loadbeam 212. Thus, one side of the load beam 212 contacts the load cell 210and another side of the load beam 212 contacts the syringe plunger 48. Aflipper 220 can extend from the arm 164 and be abutted against theplunger 48 to assure the plunger 48 always remains in contact with thepusher block 216.

In operation, the drive mechanism 20 drives the arm 164 as describedabove. This in turn drives the load beam 212 wherein the pusher block216 pushes against the plunger 48. This forces and linearly moves theplunger 48 within the barrel 46. The load cell 210 measures a reactiveforce from the force pushing against the load beam 212. The circuitryassociated with the load cell 210 converts the force to a usable signal.In a preferred embodiment, the usable signal is a voltage value. If toomuch force is required to move the plunger 48, it signifies that theinfusion line is blocked. In such a case, the voltage detected isgreater than a predetermined value, and the sensor 22 signals anocclusion in the infusion line. Thus, if the usable signal is out of apredetermined range, an occlusion is sensed. A user can then remedy thesituation.

FIGS. 15-18 disclose various aspects of the syringe sensor system 24.The system 24 generally includes a syringe plunger position sensor 230and a syringe barrel size sensor 232. FIGS. 15-17 disclose the syringeplunger position sensor 230. The sensor 230 is generally anelectromagnetic sensor that includes a magnet 234 and a plunger linearsensor array 236. The magnet 234 is mounted generally on the arm 164 ofthe connecting linkage 156 of the drive mechanism 20. The magneticsensor in the form of a linear sensor array 236 has a plurality ofsensors 238 in the form of magnets that are positioned directly adjacentto the linear path of the plunger movement. The magnet 234 has amagnetic field associated therewith. As shown in FIG. 16-17, the sensors238 detect the orientation of the field lines in the magnetic field. Theresulting signal is typically a sine wave. One sensor 238 has a specificlength over which it can detect plunger movement. Then, the next sensor238 will sense position. The sensors are initially calibrated whereinthe pump software can determine the location of the plunger engagementarm 164 and, therefore, the plunger, based on the signal levels detectedby each of the sensors 238. The magnet 234 is positioned substantiallyat a distal end of the plunger 48, or at the plunger head. The sensors238 are directly adjacent the syringe plunger 48. With such aconfiguration, a direct measurement of the plunger position is possiblerather than relying on indirect measurements. The sensors 238 are alsoconfigured to compensate for temperature changes as the pump 10 may beutilized in different environments.

FIG. 18 discloses the syringe barrel size sensor 232. Similar to theplunger position 30 sensor 230, the syringe barrel size sensor 232 isgenerally an electromagnetic sensor that includes a magnet 240 and abarrel linear sensor array 242. The magnet 240 is mounted on the syringebarrel clamp assembly. The linear sensor array 242 is mounted generallyadjacent thereto and has a sensor 244. Because the movement of thesyringe barrel clamp is less than the plunger movement, a single sensor244 can be used. Similar to the syringe plunger position sensor, basedon the signal levels sensed by the sensor 244, the sensor 232 candetermine what size syringe is loaded into the pump 10.

In operation, the pump 10 is mounted on a support structure such as apole in either a horizontal or vertical configuration as shown in FIGS.3 a and 3 b. The access door 36 is opened and a syringe assembly 14 isloaded into the pump 10. As shown in FIGS. 1, 2 and 19, the syringeassembly 14 can be conveniently loaded into the pump 10 with a singlehand. Prior art pumps require both hands of a user to load the syringe.As shown in FIG. 2, the curved lip 50 allows the syringe 14 to slideeasily into the syringe compartment 34. As shown in FIG. 19, the rollers56,58 associated with the syringe barrel clamp 52 allows the clamp 52 toslide upwards along the housing 12 in accepting the syringe 14 as in asnap-fit arrangement. When the syringe 14 is further inserted, the clamp52 is biased back onto the syringe barrel 46. The infusion line isattached to the syringe and connected intravenously to a patient. Theaccess door 36 is locked. The operating parameters of the pump 10 areloaded into the pump software through the user interface 16. Theinfusion therapy can then be started.

The pump 10 can be equipped with several different features to enhanceits operability. For example, the pump can accommodatepatient-controlled analgesia (PCA). To that end and as shown in FIG. 2,the pump 10 can have a PCA button 299 wherein a user can further controlthe infusion therapy wherein the user can push the button to deliveradditional doses of medication. The PCA button typically has a cord thatcan be plugged into the pump 10 as is generally known. The button 299can be specially designed to be activated by a thumb of a patient. Asfurther shown in FIG. 2, the button 299 can also be equipped with afingerprint reader 301 to assure only the patient can activate the PCAbutton 299. The fingerprint reader 301 is operably connected to the userinterface 16. The patient's fingerprint or thumbprint can be pre-loadedinto the pump software of the user interface 16. When the PCA button 299is pushed, and the reader 301 reads the thumbprint, the softwareverifies the button 299 was pushed by the patient by comparing the printthat was read with the stored thumbprint. The PCA button 299 can haveperipheral structure to protect inadvertent actuation. The PCA button299 can also be lighted so as so glow in the dark to aid patients inlocating the button.

FIGS. 31-33 disclose additional features associated with the PCA button299. FIGS. 31 and 32 show wiring diagrams 300 and 301 for the PCAbutton. Wiring diagrams 300 and 301 include a first circuit 302, asecond circuit 304, a third circuit 306, a common ground 308, and a4-pole push button 310 carried by the PCA button 299. FIG. 31 shows awiring diagram 300 having the push button 310 in an at rest position.FIG. 32 shows wiring diagram 301 having the push button 310 in anactuated position. As shown in FIGS. 31 and 32, circuits 302, 304, and306 share a common ground 308. Though a common ground 308 is thesimplest way to wire circuits 302, 304, and 306, it is not required forthe invention that the circuits 302, 304, and 306 share a common ground308, as long as the circuits are able to provide signals to amicroprocessor associated with the pump user interface 16. Circuits 302,304, and 306 are designed to provide a status change in signal to themicroprocessor. The status change may occur due to the installation ofthe PCA button 299 and associated wiring 312. The status change may alsooccur due to a circuit being connected to ground through push button 310versus when the circuits are open. Wiring 312 may be enclosed in acable.

Circuits 302, 304, and 306 are maintained at an energized state when notconnected to ground 308 through button 310. Conversely, circuits 302,304, and 306 are at a ground state when connected to ground 308 throughbutton 310. For example, circuits 302, 304, and 306 may maintain a smallpositive voltage when not connected to ground 308 through button 310.The small positive voltage may be coordinated with desired input signalsfor the microprocessor while considering the safety requirements of themedical environment.

As circuits 302, 304, and 306 are maintained at an energized state, alsoknown as a “HIGH” state, when not connected to ground, the circuits willall be in a HIGH state when button 310 is not installed. Installationmay involve connecting the button 310 to the wiring 312. Installationmay also involve connecting the PCA button 299, and therefore,pushbutton 310 and wiring 312 to infusion pump 10.

Wiring diagram 300 shows push button 310 in an at rest installedposition. When button 310 is in the at rest installed position, firstcircuit 302 is connected to ground directly through wiring 312 andthrough contacts 310 b and 310 a and is therefore in the ground state,or “LOW” state. When button 310 is in the actuated position as shown inwiring diagram 301, first circuit 302 is still connected to grounddirectly through wiring 312 and through contacts 310 c and 310 d and istherefore in the LOW state as long as button 310 is installed.

When button 310 is in the at rest installed position, second circuit 304is connected to ground 308 through contact 310 a and is therefore in theLOW state. When button 310 is in the actuated position as shown inwiring diagram 301, second circuit 304 is not connected to ground 308and is therefore in the HIGH state.

When button 310 is in the at rest installed position, third circuit 306is not connected to ground 308 and is therefore in the HIGH state. Whenbutton 310 is in the actuated position as shown in wiring diagram 301,third circuit 306 is connected to ground through contacts 310 c and 310d and is therefore in the LOW state.

FIG. 33 shows a table 400 summarizing information provided by the statussignals of the three PCA circuits 302, 304, and 306 of FIGS. 31 and 32.Table 400 shows that the PCA button is not installed if circuits 302,304, and 306 are all providing a HIGH status signal. If first circuit302 and second circuit 304 are providing a LOW status signal, whilecircuit three is providing a HIGH status signal, the button 310 isinstalled and is in the rest position. If first circuit 302 and thirdcircuit 306 are providing a LOW status signal, while second circuit 304is providing a HIGH status signal, the button 310 is installed and isactuated. Various other combinations of status signals indicate that afault exists. Potential faults include, but are not limited to, cablefailures, switch malfunctions, and electronic circuit malfunctions.Thus, if one of the wires associated with the PCA button 299 becomesfrayed and eventually breaks, a specific reading can be sensed by theuser interface to indicate the PCA button 299 requires replacement.

The pump 10 can also be designed with enhanced communicationcapabilities. For example, the pump 10 can communicate wirelessly withother devices such as a pharmacy computer or personal digital assistants(PDA) carried by hospital personnel. The pump 10 can also be monitoredremotely such as from a nurse's station. The pump 10 can be equippedwith various types of readers to receive patient information such asfrom swipe cards or bar-coded identification bracelets. The pump 10 mayalso utilize RFID readers and tags as discussed above.

In one preferred embodiment of the invention, the pump 10 cancommunicate with a PDA 500 as shown in FIG. 2. The pump 10 has theinfrared data port 76 that is operably coupled with the user interface16 of the pump 10. The user interface 16 has memory that storesinformation regarding pump history such as medications delivered,dosage, time, date etc. The information stored by the user interface 16can be electronically transferred to the PDA 500 carried, for example,by medical personnel. For example, the history button 74 can bedepressed on the pump control panel indicating a desire to download pumphistory. The pump 10 will prompt the user for a password on the videodisplay 60. The password may be necessary for certain regulatoryrequirements. The pump 10 will then prompt the user for a patientidentification number so the proper pump history can be identified. Thepump 10 then prompts the user to position the PDA 500 up to the dataport 76. Once positioned properly, the pump 10 downloads the proper pumphistory to the PDA 500. The user can then view the data on the PDA 500,print the pump history or sync the data to another computer as desired.The data can be formatted to be in paginated form.

The pump 10 may also communicate directly to a printer. In oneembodiment, a hand-held printer having an appropriate data port, can beheld up to the data port 76 of the pump 10. Via infrared communication,data can be transferred from the pump 10 and printed by the hand-heldcomputer.

As discussed, the pump 10 provides several advantages. The pump 10 canbe powered by either a rechargeable battery unit or a disposable batteryunit as is desired by the. user. Separate pumps are not required.Because the pump 10 can be powered by battery units, the pump 10 can beused in locations where there are limited electrical outlets.Furthermore, because the transformer for recharging the batteries iscontained within the rechargeable battery unit rather than the pump, therechargeable battery unit can be recharged simply by plugging the unitinto a wall outlet. The pump is not required. Accordingly, the pump 10can be equipped with a second unit and remain in use while the firstunit is being recharged. Also, the transformer is better stored withinthe battery unit housing rather than being located at the end of thepower cord. The syringe loaded is improved as a syringe assembly can beeasily loaded with a single hand. The syringe sensors are improved andare more reliable. The sensors provide a direct measurement of, forexample, plunger position rather than an indirect measurement. Themagnet and sensors are positioned directly at the syringe plungerproviding a direct measurement of plunger position. The sensor systemhas fewer parts in general and does not utilize additional moving partsthat are subject to wear. This improves reliability. The rotary nutassociated with the drive mechanism provides a more smooth and reliablemechanism.

While the specific embodiments have been illustrated and described,numerous modifications can be made to the present invention, asdescribed, by those of ordinary skill in the art without significantlydeparting from the spirit of the invention. The breadth of protectionafforded this invention should be considered to be limited only by thescope of the accompanying claims.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

The invention is claimed as follows:
 1. An infusion pump comprising: ahousing including a compartment structured to receive a syringe, thesyringe including a syringe barrel and a syringe plunger moveable withinthe syringe barrel; a drive mechanism supported by the housing, thedrive mechanism structured and arranged to contact the syringe plungerand move the syringe plunger within the syringe barrel; and a syringeplunger position sensor including a magnet positioned on the drivemechanism, a magnetic sensor array supported by the housing andpositioned adjacent to the magnet, the magnetic sensor array configuredto generate an output indicative of a magnetic field associated with themagnet, and software installed on the pump and configured to use theoutput to determine a linear position of the syringe plunger within thesyringe barrel.
 2. The infusion pump of claim 1, wherein the drivemechanism includes a motor, a lead screw rotatably coupled to the motor,and a connecting linkage operably connected to the lead screw, whereinrotation of the motor causes the lead screw to rotate and move theconnecting linkage to thereby move the syringe plunger within thesyringe barrel, wherein the magnet is coupled to the connecting linkage.3. The infusion pump of claim 2, wherein the magnet is coupled to asyringe plunger engagement member of the connecting linkage.
 4. Theinfusion pump of claim 2, wherein the connecting linkage includes anocclusion sensor configured to determine if an infusion line connectedto the syringe barrel is blocked.
 5. The infusion pump of claim 4,wherein the connecting linkage includes a plunger engagement memberconfigured to engage an end of the syringe barrel, the plungerengagement member including the occlusion sensor.
 7. The infusion pumpof claim 1, wherein the magnetic sensor array is a linear array ofmagnetic sensors.
 8. The infusion pump of claim 1, wherein the magneticsensor array is configured to compensate for temperature changes.
 8. Theinfusion pump of claim 1, wherein the magnetic sensor array detects theorientation of magnetic field lines associated with the magnet.
 9. Theinfusion pump of claim 1, wherein the magnetic sensor array isconfigured to produce a sine wave signal to determine the linearposition of the plunger within the syringe barrel.
 10. The infusion pumpof claim 1, the wherein the magnetic sensor array is positioned on thehousing.
 11. The infusion pump of claim 1, wherein the syringe plungerposition sensor includes an electromagnetic sensor.
 12. An infusion pumpoperable with a syringe having a syringe barrel and a syringe plungermoveable within the syringe barrel, the infusion pump comprising: ahousing including a compartment structured to receive the syringe anddefining a wall, and a syringe clamp moveable towards and away from thewall, the syringe contacting the syringe barrel when the syringe clampis moved towards the wall, a drive mechanism supported by the housing,the drive mechanism structured and arranged to contact and end of thesyringe plunger so as to be able to move the syringe plunger within thesyringe barrel; and a syringe barrel size sensor including a magnetoperably coupled to the syringe clamp, and a sensing member supported bythe housing and configured to generate an output indicative of amagnetic field associated with the magnet, and software installed on thepump and configured to use the output to determine a size of the syringebarrel received by the compartment.
 13. The infusion pump of claim 12,wherein the magnet is positioned on the syringe clamp.
 14. The infusionpump of claim 12, wherein the sensing member includes a plurality ofelectromagnetic sensors.
 15. The infusion pump of claim 12, wherein thesensing member includes a linear sensor array.
 16. The infusion pump ofclaim 12, wherein the sensing member is a single electromagnetic sensor.17. An infusion pump method comprising: sensing a magnetic fieldassociated with a first magnet coupled to a syringe clamp to determine asize of a syringe barrel received in a housing of an infusion pump; andsensing a magnetic field associated with a second magnet to determine alinear position of a syringe plunger moveable inside the syringe barrel.18. The infusion pump method of claim 17, which includes linearlysensing the magnetic field associated with the first magnet to determinethe size of the syringe barrel.
 19. The infusion pump method of claim17, which includes linearly sensing the magnetic field associated withthe second magnet to determine the linear position of the syringeplunger moveable inside the syringe barrel.
 20. The infusion pump methodof claim 17, which includes sensing an orientation of magnetic fieldlines associated with (i) the first magnet and (ii) the second magnet todetermine (a) the size of the syringe barrel and (b) the linear positionof the syringe plunger moveable within the syringe barrel, respectively.